Microelectronic device with heating electrodes

ABSTRACT

The invention relates to different designs of a microelectronic device comprising heating electrodes (HE) and field electrodes (FE) that have effect in the same sub-region of a sample chamber. By applying appropriate voltages to the field electrodes (FE), an electrical field (E) can be generated in the sample chamber. By applying appropriate currents to the heating electrodes (HE), the sample chamber can be heated according to a desired temperature profile. The heating electrodes (HE) may optionally be operated as field electrodes such that they generate an electrical field in the sample chamber, too.

FIELD OF THE INVENTION

The invention relates to a microelectronic device for manipulating a sample, comprising a sample chamber and at least one heating or mixing electrode. Moreover, it relates to the use of such a microelectronic device as a biosensor.

Biosensors often need a well controlled temperature to operate, for example because many biomolecules are only stable in a small temperature window (usually around 37° C.) or become de-activated when temperatures are outside of this temperature window. Temperature regulation is especially of high importance for hybridization assays. In these assays temperature is often used to regulate stringency of the binding of a DNA strand to its complementary strand. A high stringency is required when for instance single point mutations are of interest. Melting temperature ranges (i.e. denaturing of DNA strands) for single point mutation hybridizations can differ by less than 5° C. as compared to the wild types. A control over stringency during hybridization can give extra flexibility to especially multi-parameter testing of DNA hybridization, for example on a DNA micro-array. In these assays one also wants to ramp up temperature in a well controlled way to distinguish between mutations in a multiplexed format.

In the U.S. Pat. No. 6,864,140 B2, some of the aforementioned problems are addressed by local heating elements in the form of a thin film transistor formed on polycrystalline silicon on a substrate adjacent to a sample chamber where (bio-)chemical reactions take place. A further manipulation of the sample in the sample chamber is however not possible with this known device. Moreover, the U.S. Pat. No. 6,876,048 B2 discloses a microelectronic biosensor in which a microchip with an array of sensor elements is disposed on a membrane with heating elements. The membrane allows to control the temperature in an adjacent sample chamber in the same way for all sensor elements.

BACKGROUND OF THE INVENTION

Based on this situation it was an object of the present invention to provide means for a more versatile manipulation of a sample in a microelectronic device.

This objective is achieved by a microelectronic device according to claim 1 and a use according to claim 48. Preferred embodiments are disclosed in the dependent claims.

The microelectronic device according to a first aspect of the present invention is intended for the manipulation of a sample, particularly a liquid or gaseous chemical substance like a biological body fluid which may contain particles. The term “manipulation” shall denote any interaction with said sample, for example measuring characteristic quantities of the sample, investigating its properties, processing it mechanically or chemically or the like. The microelectronic device comprises the following components:

a) A sample chamber in which the sample to be manipulated can be provided. The sample chamber is typically an empty cavity or a cavity filled with some substance like a gel that may absorb a sample substance; it may be an open cavity, a closed cavity, or a cavity connected to other cavities by fluid connection channels. b) At least one heating electrode for exchanging heat with at least a sub-region of the sample chamber when being driven with electrical energy. As the name “heating electrode” indicates, the electrode preferably converts electrical energy into heat that is transported into the sample chamber. It is however also possible that the heating electrode absorbs heat from the sample chamber and transfers it to somewhere else under consumption of electrical energy. c) At least one field electrode for generating an electrical field in said sub-region of the sample chamber when an electrical potential is applied to said field electrode. d) A control unit for selectively driving the heating electrode and the field electrode, i.e. for supplying electrical energy to the heating electrode and for applying a potential to the field electrode.

It should be noted that the existence of an “electrical field in a sub-region of the sample chamber” or a “heat exchange with a sub-region of the sample chamber” is assumed if such a field/exchange is strong enough in the sub-region to provoke desired/observable reactions of the sample to be manipulated. This definition shall exclude small “parasitic” electrical fields and thermal effects that are inevitably associated with any (moving) electrical charge in the electrodes. Typically, a heat flow in the sense of the present invention is larger than 0.01 W/cm² and will have a duration in excess of 1 millisecond, and the strength of electrical fields in the sense of the present invention is larger than 1000 V/m.

The aforementioned microelectronic device has the advantage that the same sub-region of the sample chamber can be temperature-controlled via the heating electrode and subjected to an electrical field by which a sample in said sub-region can be manipulated in desired ways (e.g. inducing flow of a fluid and/or movement of particles).

A. Electrode Layers

In the following, embodiments of the microelectronic device according to the first aspect of the invention are described that are all based on an arrangement of the electrodes in layers.

More particularly, in these embodiments the heating electrode is disposed in a first layer, which will be called “heating layer” in the following, and the field electrode is disposed in a second layer, which will be called “field layer” in the following, wherein said layers are arranged one upon the other and adjacent to the sample chamber. The arrangement of the heating and the field electrodes in different, stacked layers has the advantage that each type of electrode can be designed in its optimal layout, for example with optimal distances between neighboring electrodes. The layers are geometrically two-dimensional and may be planar or optionally have a three-dimensional shape.

In the aforementioned embodiment, the field layer is preferably disposed between the sample chamber and the heating layer. Thus it will be as close as possible to the sample chamber, which guarantees that a maximal strength/gradient of the electrical field can be achieved there.

In another embodiment, the heating layer comprises a plurality of heating electrodes and the field layer comprises a plurality of field electrodes, wherein the electrodes of these different two layers are preferably aligned with respect to each other. Due to said alignment, the heating and the field electrodes interact similarly at different locations, thus providing uniform/periodic conditions across the area of the layers.

The aforementioned alignment may optionally comprise the situation that the field electrodes are at least partially disposed above the gaps between the heating electrodes. Here and in the following, the term “above” relates to an arbitrarily chosen orientation in which the field layer is vertically above the heating layer. Moreover, the term “partially” means that this positioning above the gaps may only be true for some (but not for all) field electrodes and/or that this condition holds only for a part of a field electrode but not the whole electrode.

Another kind of alignment may comprise the situation that the field electrodes are at least partially disposed above the heating electrodes. This design may be combined with the aforementioned design if for example some field electrodes are located above gaps and some above heating electrodes, or if a part of a field electrode is located above a gap and the rest above a heating electrode.

While the aforementioned two embodiments imply that the field electrodes run at least partially parallel to the heating electrodes, another embodiment comprises that the field electrodes are at least partially arranged at an angle to the heating electrodes. Preferably said angle is a right angle of 90°, i.e. the field electrodes run orthogonally to the heating electrodes.

B. Array of Heating Electrodes

In the following, embodiments of the microelectronic device according to the first aspect of the invention will be discussed that are based on the existence of an array of heating electrodes. It should be noted that analog embodiments can be realized mutatis mutandis with an array of field electrodes. In the most general sense, an “array of heating electrodes” simply denotes an arbitrary three-dimensional arrangement of a plurality of heating electrodes. Typically such an array is however two-dimensional and preferably planar, and the heating electrodes are arranged in a regular pattern, for example a grid or matrix pattern.

According to a preferred embodiment of the aforementioned microelectronic device, the control unit is located outside the array of heating electrodes and connected to the heating electrodes by power lines that can selectively carry electrical energy to (or from) the heating electrodes. As the amount or rate of transferred electrical energy determines the extent to which heat is exchanged with the sample chamber, the control unit has to allocate the transferred electrical energy appropriately in order to achieve a desired temperature profile in the sample chamber. The heating array can be kept most simple in this approach because the heating electrodes just have to convert electrical energy into heat without further processing. The control unit is preferably adapted to drive the heating electrodes such that a desired spatial and/or temporal temperature profile is achieved in the sample chamber. This allows to provide optimal (particularly non-uniform and/or dynamic) conditions for the manipulation of e.g. a sensitive biological sample.

In a further development of the aforementioned embodiment, the control unit comprises a de-multiplexer for coupling the control unit to the power lines. This allows to use one circuit for providing several power lines (subsequently) with electrical power.

In another realization of a microelectronic device with an array of heating electrodes, each heating electrode is associated with a local driving unit. Such local driving units can take over certain control tasks and thus relieve the control unit and in addition can increase the efficiency of the array by avoiding leakage of driving currents between e.g. an external current source and an array of heating electrodes.

According to a further development of the aforementioned embodiment, said driving units are coupled to a common power supply line, and the heating electrodes are coupled to another common power supply line (e.g. ground). In this case the local driving unit determines the amount of electrical energy or power that is taken from the common power supply lines. This simplifies the design insofar as properly allocated amounts of electrical energy do not have to be transported through the whole array to a certain heating electrode.

In another embodiment of the microelectronic device with an array of heating electrodes, which may advantageously be combined with the aforementioned design, a part of the control unit is located outside the array of heating electrodes and connected via control lines for carrying control signals to local driving units (which constitute the residual part of the control unit). Said local driving units are located at the heating electrodes and coupled to them. In this case the mentioned outside part of the control unit can determine how much electrical energy or power a certain heating electrode shall receive; this energy/power needs however not to be transferred directly from the outside control unit to the heating electrode. Instead, only the associated information has to be transferred via control signals to the local driving units, which may then extract the needed energy/power from common power supply lines.

In another realization of the aforementioned embodiment, the control signals are pulse-width modulated (PWM). With such PWM signals, the local driving units can be switched off or on with selectable rate and duty cycle, wherein these parameters determine the average power extraction from common power supply lines. The individual characteristics of the local driving units are then less critical as only an on/off behavior is required. It is also possible to drive the heaters or field electrodes with pulse amplitude modulation (PAM), pulse frequency modulation (PFM) or a combination of modulation techniques.

In a further development of the aforementioned embodiments, the local driving units comprise a memory for storing information of control signals transmitted by the outside part of the control unit. Such a memory may for example be realized by a capacitor that stores the voltage of the control signals. The memory allows to continue a commanded operation of a heating electrode while the associated control line is disconnected again from the driving unit and used to control other driving units.

C. Bi-Functional Electrode

In the following, embodiments of the microelectronic device according to the first aspect of the invention will be discussed that are based on field electrodes that can also be operated as heating electrode. Due to this fact, such field electrodes will be called “bi-functional electrodes” in the following.

Such a microelectronic device may comprise several bi-functional electrodes. Preferably, all electrodes of the microelectronic device are bi-functional electrodes, i.e. they may be used for the generation of electrical fields as well as for a heat exchange with the sample chamber.

The bi-functional electrode may by definition be operated as a field electrode for generating an electrical field and as a heating electrode for exchanging heat with the sample chamber. It may particularly fulfill these two functions subsequently. According to a preferred embodiment, the control unit is however adapted to drive the bi-functional electrode simultaneously as a field electrode and a heating electrode; the bi-functional electrode will then at the same time generate an electrical field and exchange heat with the sample chamber. Of course a mixed operation is also possible in which the bi-functional electrode may at times be operated exclusively as field electrode, exclusively as heating electrode, or simultaneously as field and heating electrode.

There are many different ways to realize a bi-functional electrode. In a particular simple design, the bi-functional electrode is connected with one pole to a first electrical potential and, via a switch that is controlled by the control unit, with its second pole to a distinct second electrical potential (wherein an electrode is in general assumed to have two poles or ends for connecting it to different electrical potentials). When the switch is opened, the electrode floats at the first potential; when the switch is closed, a current according to the difference between the first and second potential will flow through the electrode.

D. Miscellaneous Embodiments

In the following, several further particular embodiments of the present invention will be described that can be realized in connection with microelectronic devices according to the first aspect of the invention.

Thus the microelectronic device may comprise at least two field electrodes which commonly generate an electrical field in the sub-region of the sample chamber when an electrical voltage is applied between them. Using cooperating pairs of two field electrodes allows a very precise control of the generated electrical field.

It was already mentioned that the heating electrode is in most cases capable of generating heat. In an optional embodiment, the heating electrode may however also be adapted to remove heat from the sample chamber. Such a removal may for example be achieved by coupling the heating electrode to a heat sink or by cooling it with a fan. In these cases, the heating electrode may internally still generate heat, which is however less than the heat that it is absorbed by the heat sink, thus resulting in a net absorption of heat.

The heating electrode may particularly be realized by a resistive strip, a transparent electrode, a Peltier element, a radiofrequency heating electrode, or a radiative heating (IR) element. All these elements can convert electrical energy into heat, wherein the Peltier element can additionally absorb heat and thus provide a cooling function.

The microelectronic device may optionally comprise at least one temperature sensor which makes it possible to monitor the temperature in the sample chamber. Preferably, the microfluidic device comprises a plurality of temperature sensors. In another preferred embodiment, said temperature sensor is comprised in the heating layer. In a particular embodiment, the heating electrode may be operated as a temperature sensor, which allows to measure temperature without additional hardware.

In cases in which a temperature sensor is available, the control unit is preferably coupled to said temperature sensor and adapted to control the heating electrodes in a closed loop according to a predetermined (temporal and/or spatial) temperature profile in the sample chamber. This allows to provide robustly optimal conditions for the manipulation of e.g. a sensitive biological sample.

The microelectronic device may further comprise a micromechanical device or an electrical device, for example a pump or a valve, for controlling the flow of a fluid and/or the movement of particles in the sample chamber. Controlling the flow of a sample or of particles is a very important capability for a versatile manipulation of samples in a microfluidic device.

In a particular embodiment, the heating electrode may be adapted to create flow in a fluid in the sample chamber by a thermo-capillary effect. Thus its heating capability can be exploited for moving the sample.

Moreover, the field electrodes can be used to generate movement of particles or liquid via AC or DC electro-osmosis, electrophoresis, dielectrophoresis, electrohydrodynamics and/or a combination of these effects. In the case of dielectrophoresis real bio-particles in the sample maybe too small for manipulation and therefore larger diameter particles with the desired electrical properties may be added to the liquid to facilitate mixing.

The microelectronic device may optionally comprise a sensor element, preferably an optical, magnetic or electrical sensor element for sensing properties of a sample in the sample chamber. A microelectronic device with magnetic sensor elements is for example described in the WO 2005/010543 A1 and WO 2005/010542 A2. Said device is used as a microfluidic biosensor for the detection of biological molecules labeled with magnetic beads. It is provided with an array of sensor units comprising wires for the generation of a magnetic field and Giant Magneto Resistance devices (GMRs) for the detection of stray fields generated by magnetized beads.

According to a preferred embodiment of the invention, the microelectronic device comprises a “heating array” of several heating electrodes and a “sensing array” of several sensor elements (including the aforementioned sensor elements and/or temperature sensors mentioned above), wherein the heating electrodes are aligned with respect to the sensor elements. This “alignment” means that there is a fixed (translation-invariant) relation between the positions of the heating electrodes in the heating array and the sensor elements in the sensing array; the heating and sensor elements may for example be arranged in pairs, or each heating electrode may be associated with a group of several sensor elements (or vice versa). The alignment has the advantage that the heating and sensor elements interact similarly at different locations. Thus uniform/periodic conditions are provided across the arrays.

A preferred kind of alignment between the sensor and the heating electrodes is achieved if the patterns of their arrangement in the sensing array and the heating array, respectively, are identical. In this case, each sensor element is associated with just one heating electrode.

In an alternative embodiment, more than one heating electrode is associated to each sensor element. This allows to create a spatially non-uniform heating profile, which can result in either a spatially non-uniform or a spatially uniform temperature profile in the region of one sensor element and thus an even better temperature control. Preferably, there is additionally an alignment of the above mentioned kind between heating electrodes and sensor elements.

If it is necessary or desired to have sub-regions of different temperature in the sample chamber, this may optionally be achieved by dividing the sample chamber with a heat insulation into at least two compartments.

Between the sample chamber and the field electrodes, a partially electrical isolating layer and/or a biocompatible layer may be disposed. Such a layer may be a hydrogel material such as polyacrylamide or polyimide.

Between the field and heater electrode layers an isolating layer may be disposed. Such a layer may for example consist of polyimide, silicon dioxide SiO₂ or the photoresist SU8.

It was already mentioned that the heating electrodes and field electrodes may be arranged in separate layers at one side of the sample chamber. The heating electrode(s) and field electrode(s) may however also be disposed on vertically opposing sides of the sample chamber (including the case that there are additionally some heating electrodes and field electrodes which are located at the same side of the sample chamber).

The microelectronic device may particularly comprise a plurality of field electrodes that are arranged parallel to each other in a layer and that are connected to the control unit at alternating ends. This means that one field electrode is connected at its left end to the control unit, the next at its right end, the next but one again at its left end and so on. This alternating scheme provides at both sides a maximum of space to make the connections.

The heating electrode and/or the field electrode may be straight or non-straight (i.e. curved or bent). Examples of these designs will be discussed with respect to the Figures in more detail.

The electrodes may further be rectangular, tapered and/or asymmetric in their shape and/or in their cross section. Tapered field electrodes may for example be advantageous with respect to the concentration of electric field lines.

Furthermore, the heating electrode and/or the field electrode may consist of several parallel leads. These leads are preferably connected at one end, thus forming a common pole of the electrode.

Moreover, the field electrodes may optionally be arranged as a quadrupole. Such a design may be advantageous for concentrating particles at a certain focus-location of a sample.

The distance between neighboring field electrodes is preferably less than 50 μm, most preferably less than 10 μm. These distances allow to generate electrical fields of high strength and gradient.

Moreover, the microelectronic device may comprise several heating electrodes arranged in parallel, wherein the distance between neighboring heating electrodes is larger than 50 μm, preferably larger than 100 μm.

In a further embodiment of the invention, the control unit is adapted to drive the heating electrode with an alternating current of selectable intensity and/or frequency. The electrical fields associated with such an operation of the heating electrodes may in certain cases, for example in cases of dielectrophoresis, generate a motion in the sample if they have an appropriate intensity and frequency. On the other hand, the intensity and frequency of the alternating current determines the average rate of heat production. Thus it is possible to execute the heating and the manipulation function of such an electrode simply by changing the intensity and/or frequency of the applied current appropriately. In particular at the cross-over frequency the dielectrophoretic force is zero and so no particle movement will be induced. In essence only heating will occur when this frequency of field is applied. This is of particular interest if mixing particles have been added as they have a well defined diameter and electrical properties and thus also a well defined zero frequency.

The heating electrode(s) and/or field electrode(s) may preferably be realized in thin film electronics.

In the following, some preferred embodiments will be described which are based on a microelectronic device that comprises a “heating array” with a plurality of heating electrodes and/or a “field array” with a plurality of field electrodes, wherein said arrays may optionally be merged.

When realizing such a device, a large area electronics (LAE) matrix approach, preferably an active matrix approach may be used in order to contact the electrodes. The technique of LAE, and specifically active matrix technology using for example thin film transistors (TFTs) is applied for example in the production of flat panel displays such as LCDs, OLED and electrophoretic displays.

In the aforementioned embodiment, a line-at-a-time addressing approach may be used to address the electrodes by the control unit.

According to a further development of the microelectronic device with arrays of heating and/or field electrodes, the interface between the sample chamber and said arrays is chemically coated in a pattern that corresponds to the patterns of the electrodes. Thus the effect of the electrodes can be combined with chemical effects.

In the aforementioned embodiment, binding molecules may for example be attached to the interface at locations where a sample substance can be trapped by electrical fields of the field electrodes. Thus the field electrodes can assist the process of binding a sample to the interface for further analysis. There afterwards the polarity of the force can be reversed to remove non-bonded material.

In another embodiment of the microelectronic device with arrays of field and/or heating electrodes, each heating electrode and/or field electrode is locally associated to an addressing element, a driving unit, a memory unit and/or a frequency oscillator. The oscillator may particularly be a tunable oscillator, preferably a relaxation oscillator or a ring oscillator.

The invention further relates to the use of the microelectronic devices described above for molecular diagnostics, biological sample analysis, or chemical sample analysis, food analysis, and/or forensic analysis. Molecular diagnostics may for example be accomplished with the help of magnetic beads or fluorescent particles that are directly or indirectly attached to target molecules.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. These embodiments will be described by way of example with the help of the accompanying drawings in which:

FIG. 1 shows schematically a section through a microelectronic device with stacked layers of heating electrodes and field electrodes;

FIGS. 2 and 3 show a microelectronic device like that of FIG. 1 when additional electrical fields are generated by bi-functional heating electrodes;

FIG. 4 shows a variant of the device of FIG. 1, wherein a counter electrode is located at the opposite side of the sample chamber;

FIGS. 5-7 show different designs of the sample chamber with a substrate and electrodes on both sides;

FIGS. 8 and 9 show schematically views of a substrate with two vertically stacked electrode layers that are aligned with respect to each other;

FIGS. 10 and 11 show alternative approaches for connecting electrodes in large area electronics by VIAs;

FIG. 12 shows schematically a top view of a patterned layer of bi-functional electrodes;

FIG. 13 shows two alternative circuits for applying alternatively current or voltage to a bi-functional electrode;

FIG. 14 shows schematically an active matrix heater array with the heater driver circuitry outside the array;

FIG. 15 shows a variant of FIG. 14 in which a single heater driver is connected via a de-multiplexer to the array of heating electrodes;

FIG. 16 shows schematically the circuit of an active matrix heater system with local driving units;

FIG. 17 shows the design of FIG. 16 with an additional memory element;

FIG. 18 shows an active matrix system with a local oscillator;

FIGS. 19 to 26 show different designs concerning the local oscillator of FIG. 18.

Like reference numbers/characters in the Figures refer to identical or similar components.

DESCRIPTION OF THE EMBODIMENT

Biochips for (bio)chemical analysis, such as molecular diagnostics, will become an important tool for a variety of medical, forensic and food applications. In general, biochips comprise a biosensor in most of which target molecules (e.g. proteins, DNA) are immobilized on biochemical surfaces with capturing molecules and subsequently detected using for instance optical, magnetic or electrical detection schemes. Examples of magnetic biochips are described in the WO 2003/054566, WO 2003/054523, WO 2005/010542 A2, WO 2005/010543 A1, and WO 2005/038911 A1, which are incorporated into the present application by reference.

The binding-kinetics of the target molecules to the biochemical surface determine the speed and specificity of the biosensor. For low concentrations (pMol) of large biomolecules the binding-kinetics are diffusion limited, and with that the speed of high-sensitivity biosensors is limited. Electrical manipulation and local fluid control offer the ability to influence the binding-kinetics of molecules to a surface, and allow to increase the speed of measurement. It will become essential if reduced concentrations of biomarkers are to be measured. It is even conceivable to improve on the specificity of the binding by “pulling” the target molecules from the surface in a controlled way (stringency test) to remove specifically the weakly bound (a-specifically adsorbed) molecules.

A more defined way to improve the specificity of a biosensor is by control of the temperature, which is often used during a hybridization assay to regulate stringency of the binding of a target biomolecule to a functionalized surface, e.g. the binding of a DNA strand to its complementary strand. A high stringency is required when for instance single point mutations are of interest. Besides being of high importance for hybridization assays, temperature control of a biosensor is needed in general. In the literature the use of resistive electrodes for heating elements and temperature sensing elements in integrated biomedical devices has therefore been reported. More generally, the ability to control temperature AND fluids on a biochip is essential. Besides general temperature or flow management, the ability to control fluid convection locally in combination with temperature control offers options to enhance dissolution of reagents, to enhance mixing of (bio)chemicals and to enhance temperature uniformity.

In order to optimize the performance of a biosensor, elements to control the temperature as well as means for electrical fluid actuation and electrical manipulation of biomolecules need to be integrated in the biosensor. It is therefore proposed here to incorporate a temperature processing array in a biosensor and to combine it with mixing or pumping elements. Electrode arrays used for electrical particle/fluid manipulation however have typically a spacing between the electrodes smaller than 100 μm (high field strengths and field gradients are desired), often in the range of 10 μm, which leaves little lateral space for integration of temperature control elements (e.g. heaters, sensors). Hence, the problem to be solved is that electrodes for temperature control and electrodes for electrical particle or fluid manipulation cannot generally be deposited next to one another and therefore cannot be patterned from a single conductive/resistive layer.

1) Vertically Stacked Electrode Arrays

In a first series of embodiments it is proposed to use at least two vertically stacked arrays of electrodes for temperature control and electrical manipulation of fluids/biomolecules. FIG. 1 shows schematically the general setup. The heating elements or “heating electrodes” HE consist of resistive electrodes and are preferably located in the patterned electrode layer closest to the substrate SU carrying the electrodes. In addition, the “field electrodes” FE used for electrical manipulation of fluids/biomolecules are preferably positioned closest to the sample chamber SC, which is advantageous with respect to the ability to obtain high electric fields E and high gradients in electric fields in the sample. In a preferred embodiment, at least one temperature sensing element, consisting of a resistive electrode, is incorporated in at least one of the patterned electrode layers. The heating electrodes HE and field electrodes FE are coupled to a control unit CU that supplies them with appropriate voltages and/or currents.

An electrically insulating layer is present between the first and second electrode layer. A preferred technology to realize this structure is the well known “field shielded pixel” active matrix technology used for the fabrication of (reflective and transflective) LCDs, where a tough (polymeric) layer of several microns in thickness is used to separate the second metal layer from the first layer (which is generally deposited directly onto the substrate).

Besides being electrically insulating, the aforementioned layer may comprise a biocompatible topcoat. Also the field electrode layer may be covered with a partially electrically insulating layer and/or a biocompatible topcoat (e.g. polyimide, porous SiO₂, polyacrylamide). Both electrode layers may also comprise a native oxide on top of the electrodes. Additional biocompatible and/or insulating layers may be deposited on top of the stack of electrode layers.

In another embodiment, heating electrodes in the first patterned layer are sequentially used for heating and to guard the electric field created with the field electrodes FE in the second patterned layer. Due to their double function for heating and field generation, these electrodes are denoted with the reference sign FHE in FIGS. 2-4 (the heating electrodes HE shown in the other Figures may in general also be bi-functional FHE electrodes). The field generation of the FHE electrodes is advantageous as it provides an additional parameter to obtain the desired electrical field, which is particularly of relevance for the electrical manipulation of fluids/biomolecules. For instance, by setting the electrodes in the first and second layer at the same potential a more homogeneous in-plane electric field can be created (FIG. 2). On the other hand, by applying a different potential to the electrodes in the first and second layer, a vertical component of the electric field can be tuned (FIG. 3). In an additional embodiment, the electrodes FHE that are used for heating/temperature sensing AND manipulation are connected to a floating current source or can be disconnected from a current source while being connected to a voltage source.

Although the electric field may be directed in a better direction using the heating layer electrodes in addition to the field layer electrodes, the presence of the field layer (or additional layers) electrodes may reduce the intensity of the field lines that will pass through from the heating electrode. An alternative set of embodiments to reduce this effect will be to provide the field electrodes at a much smaller pitch (say 10 μm) than the heating electrodes (say 100 μm)—heat will spread in any case.

The use of the first and second layer of patterned electrodes to tune the desired electrical field strength and gradients can be expanded to multiple electrode layers. In addition, an (patterned) electrode layer used for heating may also be present on another substrate above the first mentioned substrate.

FIGS. 4-7 show a schematic representation of a sample chamber or flow channel SC enclosed by multiple substrates, of which one substrate carries at least one electrode and the other substrate carries at least two patterned electrode layers. Such a structure is particularly suited to manipulate biomolecules perpendicular to the substrates, in addition to manipulation in-plane with the substrate (FIG. 4). It should be understood that this part of the invention is not limited to the shown embodiments but can be generally applied to a wide variety of configurations.

The field and heating electrode layers are preferably aligned with respect to one another. FIGS. 8 and 9 show several specific embodiments of alignment. In these Figures it is assumed that electrodes HE (or FHE) used for heating are located in the first patterned electrode layer and electrodes FE used for electrical manipulation of fluids/biomolecules are located in the second patterned electrode layer. As will be appreciated by an expert in the field, the invention is not limited to the shown embodiments. The invention also applies to non-straight electrode configurations, such as quadrupoles or multipoles. Besides illustrating several ways of alignment, FIGS. 8 and 9 also illustrate how the individual electrodes of each of the layers can be contacted without shorts. For clarity, it is noted that heating elements HE (or FHE) and temperature sensing elements TS require at least two contacts as a current must flow through the electrodes. An electrode FE used for electrical manipulation of fluids/biomolecules requires at least one contact to bring the electrode to a certain electrical potential.

FIG. 8 shows schematic views a) to f) of a substrate with two vertically stacked patterned electrode layers that are aligned with respect to one another in a cross section (top of each drawing a-f) and a top view (bottom of each drawing a-f). More particularly, the individual drawings show:

a) and c): field electrodes FE in the second layer are positioned parallel to and in between the heating electrodes HE of the first layer with contacts to one side. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer. In drawing c), each field electrode FE consists of several parallel leads. b), d), and e): field electrodes FE in the second layer are positioned parallel to and in between the heating electrodes HE of the first layer with contacts to two opposite sides. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer. In drawings d) and e), each field electrode FE consist of several parallel leads. In drawing d), the electrodes FE are contacted in an alternating fashion from both sides, while in e) they run only to the middle of the array and thus have to be contacted at both sides. f): field electrodes FE in the second layer are positioned orthogonal to the heating electrodes HE of the first layer. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer.

FIG. 9 shows similarly schematic top views of a substrate with two vertically stacked patterned electrode layers that are aligned with respect to one another:

a), b): field electrodes FE in the second layer are positioned parallel and on top of the heating electrodes HE of the first layer with contacts to one side. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer. In drawing b), each field electrode FE consists of several parallel leads. c), d): field electrodes FE in second layer are positioned parallel and on top of the heating electrodes HE of the first layer with contacts to two opposite sides. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer. In drawing c), the electrodes FE are contacted in an alternating fashion from both sides, while in d) they run only to the middle of the array and thus have to be contacted at both sides. e): field electrodes FE in the second layer are positioned parallel and in an alternating way on top of and in between the heating electrodes HE of the first layer with contacts to two opposite sides. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer. f): field electrodes FE in the second layer are positioned in between the heating electrodes HE of the first layer with contacts to two opposite sides. Opposing electrodes in the field layer are displaced with respect to one another. The heating electrodes HE in the first layer are non-straight. The contacts of the field layer electrodes are positioned in between the contacts of the heating electrodes in the first layer.

In general terms, FIGS. 8 and 9 show that electrodes in the field and heating layer may be non-straight in order to be able to position the contacts of the individual electrodes next to one another on the same edge. Moreover, it is shown that electrodes may also be non-straight to diverge towards a different edge (e.g. FIG. 90. Optionally the non-straight lengths of the FE electrodes can be covered with an insulator to prevent them creating inhomogeneous fields in the sample space.

Besides the shown square-like shaped electrodes, various patterns may be used, such as sharpened and asymmetric electrodes, and quadrupoles. These structures are in particular advantageous for electrical manipulation of fluids/biomolceules.

The resistive heating elements may also be used to create a fluid flow using the so-called thermo-capillary effect. The fluid flow will drag with it the particles contained in the fluid. In combination with the electrical manipulation of biomolecules this can be advantageous. For instance, in case particles are trapped with the electrodes used for electrical manipulation, the heating elements can create a fluid flow and with that supply new particles. In a similar manner, a convectional flow could be introduced into the cell.

The field electrodes may be used to create a fluid flow, too. This can be achieved by moving the liquid via AC or DC electro-osmosis, electrophoresis, dielectrophoresis, electrohydrodynamics and/or a combination of these effects.

In another preferred embodiment, a large area electronics (LAE) matrix approach, even more preferably an active matrix approach (e.g. low temperature poly silicon (LTPS), amorphous-Si), is used to contact the electrodes in the first and second patterned layer. This is advantageous as it reduces the number of required input/output contacts to the outside world. Large area electronics, and specifically active matrix technology using for example Thin Film Transistors (TFT), is commonly used in the field of flat panel displays for the drive of many display effects e.g. LCD, OLED and Electrophoretic. The (metal) electrodes used for heating and/or manipulation may be additionally deposited on top of a backplane containing the active matrix electronics. In another embodiment, the metal layers used to built the active matrix components (e.g. TFTs, diodes) are also used to make one or both of the electrode layers for temperature control and/or electrical manipulation of biomolecules/fluid.

Conductive paths (vias) are needed between the active components (TFTs, diodes, capacitors) and the electrodes in the first and second layer. This is shown in FIGS. 10 and 11. The vias VIA1, VIA2 may be made from the same metal layer as deposited to make part of the active matrix components of (e.g. TFT, diode). In case the electrodes in the first and second layer are not aligned above one another, the application of vias is straightforward.

FIG. 10 shows particularly the case that electrodes in the first and second layer are aligned above one another. A via VIA1 can then be applied to connect a field electrode FE in the second layer through a hole in the heating electrode HE in the first layer with its field-control circuit FC that is located in the LAE backplane. The heating electrode HE in the first layer can be directly connected to its heating-control circuit HE in the LAE backplane by a via VIA2.

The aforementioned design is however undesirable if the electrode HE in the first layer is used for heating as the presence of the hole will locally increase the resistance and therefore the temperature. The electrode with the hole for the via can be made slightly wider to compensate for the increase in resistance of the hole. This, however, may result in unwanted current profiles and therefore temperature gradients. As shown in FIG. 11, the via VIA1 to the field electrode FE in the second layer may in that case be applied around the heating electrode HE. This may however be undesirable when the field electrodes in the second layer are used to electrically manipulate the fluids/biomolecules as the contact between via and electrode will disturb the electrical field (e.g. in a sense broaden the electrode). The problem becomes more severe when the number of field electrodes FE in the second electrode layer becomes larger. When a certain voltage (amplitude, phase, frequency) is applied to multiple electrodes at the same moment, a possible solution is to attach only one via to a multiplicity of closely spaced comb like electrodes (not shown).

Whilst FIGS. 10 and 11 show the positioning of the electronics HC, FC in the LAE backplane underneath the electrode layers, the invention is not limited to such a configuration. The electronics may also be placed next to the electrodes, or in another place where there is sufficient space and use fan in connections to the heaters, sensors and manipulation electrodes.

2) Single Electrode Layer for Temperature Control and Electrical Manipulation of Fluids/Biomolecules

In a second series of embodiments it is proposed to use a single patterned layer of electrodes FHE for both temperature control and electrical manipulation of fluids/biomolecules by sequential application of a voltage across a (resistive) electrode FHE (i.e. for heating and temperature sensing, FIG. 12 a) and between the electrodes FHE (i.e. for electrical manipulation of fluids/biomolecules, FIG. 12 b). The patterned electrode layer may be covered with a (partially) electrically insulating layer (e.g. SU-8, polyimide, SiO₂, native metallic oxide) and/or with a biocompatible layer (e.g. SU-8). Each electrode FHE has at least two contacts. At least two contacts are used in case the (resistive) electrode is used for heating or temperature sensing (FIG. 12 a). In case the electrode is used for electrical manipulation of fluids/biomolecules (FIG. 12 b), (distinct) voltages V1, V2, V3, V4 are applied via at least one contact. Applying these voltages via more than one contact (shown for the rightmost electrode in FIG. 12 b) may be advantageous in order to reduce the time it takes to put the complete electrode at the desired potential.

A single electrode can be regarded as a resistor. Alternating use of the same electrode for heating/temperature sensing and electric manipulation of fluids/biomolecules requires switching of the electric circuit connected to the electrode between applying a current through the electrode and a potential to the electrode. FIG. 13 shows two concepts to realize this. Both AC and DC signals may be applied. FIG. 13 a shows the use of one voltage source V1 with a switch T1 (e.g. transistor) between the electrode FHE (resistor) and ground GR. When the switch is closed, a current will flow through the electrode. When the switch is open, the electrode is driven to the voltage of the source. The TFT switch can also be used as a current source for heating. FIG. 13 b shows the use of two voltage sources; one V1 for heating and one V2 for manipulation. The switches T2, T3, T4 provide the necessary voltages to the electrode FHE (resistor). The voltage sources can be AC or DC. In the AC case the gates of the switches will need to be held at voltages beyond the range of the AC field. The sources may be applied from a connection to the outside.

In another embodiment, the same electrode is SIMULTANEOUSLY used for temperature control (heating, sensing) and manipulation of biomolecules/fluid. In the case of e.g. DEP (dielectrophoresis) motion, the high frequencies will or can be used to cause a heating effect. It would therefore be possible to additionally drive the single electrode to realize the following functionality:

DEP only, no heating: Use either low intensity or low duty cycle AC signal;

Heating only (no net particle movement)—high intensity AC at two frequencies for mutually compensating +DEP and −DEP; temperature control via duty cycle;

DEP at cross over frequency so only heating occurs. This is most applicable for systems with well-defined particles such as mixer particles or magnetic particles of a well-defined diameter.

Motion+heating: high intensity AC at required frequency.

The use of a single patterned electrode layer for temperature control and electrical manipulation of fluids/biomolecules already reduces the number of required I/O pins to the outside world. Preferably, the electrode array is realized using thin film electronics. In order to reduce the number of required I/O pins further and/or to integrate electronic circuits on the substrate, the array may be realized in the form of a matrix array, especially an active matrix array (e.g. LTPS, amorphous Si).

The (metal) electrodes used for heating and/or manipulation may be deposited on top of a backplane containing the active matrix electronics. In another embodiment, the metal layers used to build the active matrix components (e.g. TFTs, diodes) are also used to make the electrodes layer for temperature control and/or electrical manipulation of biomolecules/fluids.

Conductive paths (vias) are needed between the active components (e.g. TFTs, diodes) and the electrodes. The application of vias is straightforward. To be able to sequentially apply a voltage across an electrode or in between electrodes, electronic circuits may be integrated in the LAE backplane.

3) Hybridization Spots Deposited in Alignment with Electrodes

In a third series of embodiments it is proposed to align hybridization spots, typically consisting of probe molecules (e.g. single DNA strands, anti-ligands) immobilized on a surface, with the electrodes used for temperature control and electrical manipulation of fluid and biomolecules.

Generally, hybridization spots are deposited on the surface after the electrodes have been fabricated. For instance, ink-jet printing may be used to deposit DNA capturing probes. Hybridization spots can be deposited on certain positions relative to the electrodes, e.g. at trapping sites of biomolecules, and/or above temperature controlled areas. Alternatively self-assembling capture molecules can be grown on certain surfaces (e.g. Au)

Depending on the electrode structure and applied (AC, DC) voltages biomolecules can be trapped. For example, an electrode structure like that of FIG. 12 can be used to electrically smear out the various particles present in a sample using the frequency-dependent dielectrophoretic force.

The presence of hybridization spots at electrical trapping sites provides a way to keep biomolecules trapped while the voltages on the electrodes are altered. By switching voltages and/or frequencies one can switch between a negative and a positive dielectric force on a biomolecule (e.g. pull/push), which provides a simple electrical method to control the stringency of the binding and flush away any non-bonded material. Similarly, the combination of electrical and biochemical trapping is advantageous in case a single electrode layer is used for temperature control and electrical manipulation. First the electrodes can be used to trap biomolecules. Then, when the biomolecules are held on position with the hybridization spots, the same electrodes can be used to control the temperature, for instance to control the stringency of the binding.

4) Various Designs of Microfluidic Biosensors

As was already mentioned, the performance of a biosensor can considerably be improved by incorporating a programmable temperature processing array into the sensor module. The temperature processing array can be used to either maintain a constant temperature across the entire sensor area, or alternatively to create a defined temperature profile if the biosensor is also configured in the form of an array and different portions of the biosensor operate optimally at different temperatures. In all cases, the temperature processing array comprises a multiplicity of individually addressable and drivable heating elements, and may optionally comprise additional elements such as temperature sensors, mixing or pumping elements, and even the sensing element itself (e.g. a photosensor). Preferably, the temperature processing array is realized using thin film electronics, and optionally the array may be realized in the form of a matrix array, especially an active matrix array. Whilst the invention is not limited to any particular type of biosensor, it can be advantageously applied to biosensors based upon optical (e.g. fluorescence), magnetic or electrical (e.g capacitive, inductive . . . ) sensing principles. In the following, various designs of such biosensors will be described in more detail.

Each individual heating element HE, FHE may comprise any of the well known concepts for heat generation, for example a resistive strip, Peltier element, radio frequency heating element, radiative heating element (such as an Infra-red source or diode) etc. Each heating element is individually drivable, whereby a multiplicity of temperature profiles may be created.

To enhance temperature control, in particular thermal cycling, means may be provided to cool a biosensors during operation, such as active cooling elements (e.g. thin film Peltier elements), thermal conductive layers in thermal contact with a heat sink or cold mass and a fan.

5) Active Matrix Arrays of Heating Elements

As was already pointed out several times, the array of heating terminals may be realized in the form of a matrix device, preferably an active matrix device (alternatively being driven in a multiplexed manner). In an active matrix or a multiplexed device, it is possible to re-direct a driving signal from one driver to a multiplicity of heaters, without requiring that each heater is connected to the outside world by two contact terminals.

In the embodiment shown in FIG. 14, an active matrix is used as a distribution network to route the electrical signals required for the heaters from a central driver CU via individual power lines iPL to the heater elements HE. In this example, the heaters HE are provided as a regular array of identical units, whereby the heaters are connected to the driver CU via the transistors T1 of the active matrix. The gates of the transistors are connected to a select driver (in all cases a standard shift register gate driver as used for an Active Matrix Liquid Crystal Display AMLCD), whilst the source is connected to the heater driver, for example a set of voltage or current drivers. The operation of this array is as follows:

To activate a given heater element HE, the transistors T1 in the entire row of compartments incorporating the required heater are switched into the conducting state (by e.g. applying a positive voltage to the gates from the select driver).

The signal (voltage or current) on the individual power line iPL in the column where the heater is situated is set to its desired value. This signal is passed through the conducting TFT to the heater element, resulting in a local temperature increase.

The driving signal in all other columns is held at a voltage or current, which will not cause heating (this will typically be 0V or 0 A).

After the temperature increase has been realized, the transistors in the line are again set to the non-conducting state, preventing further heater activation.

As such, the matrix preferably operates using a “line-at-a-time” addressing principle, in contrast to the usual random access approach taken by CMOS based devices.

It is also possible to activate more than one heater HE in a given row simultaneously by applying a signal to more than one column in the array. It is possible to sequentially activate heaters in different rows by activating another line (using the gate driver) and applying a signal to one or more columns in the array.

Whilst in the embodiment of FIG. 14 a driver is considered that is capable of providing (if required) individual signals to all columns of the array simultaneously, it would also be feasible to consider a more simple driver with a function of a de-multiplexer. This is shown in FIG. 15, wherein only a single output driver SD is required to generate the heating signal (e.g. a voltage or a current). The function of the de-multiplex circuit DX is simply to route the heater signal to one of the columns, whereby only the heater is activated in the selected row in that column. Alternatively, the dc-multiplexer DX could be directly attached to a plurality of heating elements (corresponding to the case of only one row in FIG. 15). The function of the de-multiplex circuit is then simply to route the heater signal to one of its outputs, whereby only the desired heater is activated.

A problem with the simple approach of individually driving each heating element through two contact terminals is that an external driver is required to provide the electrical signals for each heater (i.e. a current source for a resistive heater). As a consequence, each driver can only activate a single heater at a time, which means that heaters attached to the same driver must be activated sequentially. This makes it difficult to maintain steady state temperature profiles. Furthermore, if a driving current is required, it is not always possible to bring the current from the driver to the heater without a loss of current, due to leakage effects.

For this reason, it may be preferred to use the active matrix technology to create an integrated local heater driver per heating element. FIG. 16 illustrates such a local driver CU2 which forms one part of the control unit for the whole array; the other part CU1 of said control unit is located outside the array of heating electrodes HE (note that only one heating electrode HE of the whole array is shown in FIG. 16). Now every heater element HE comprises not only a select transistor T1, but also a local current source. Whilst there are many methods to realize such a local current source, the most simple embodiment requires the addition of just a second transistor T2, the current flowing through this transistor being defined by the voltage at the gate. Now, the programming of the release signal is simply to provide a specified voltage from the external voltage driver CU1 via individual control lines iCL and the select transistor T1 to the gate of the current source transistor T2, which then takes the required power from a common power line cPL.

In a further embodiment shown in FIG. 17, the local driver CU2 can be provided with a local memory function, whereby it becomes possible to extend the drive signal beyond the time that the compartment is addressed. In many cases, the memory element could be a simple capacitor C1. For example, in the case of a current signal, the extra capacitor C1 is situated to store the voltage on the gate of the current source transistor T2 and maintain the heater current whilst e.g. another line of heater elements is being addressed. Adding the memory allows the heating signal to be applied for a longer period of time, whereby the temperature profile can be better controlled.

Whilst all the above embodiments consider the use of thin film electronics (and active matrix approaches) to activate the heating elements, in the most simple embodiment, the individual heating elements may all be individually driven, for example in the case of a resistive heating element by passing a defined current through the element via the two contact terminals. Whilst this is an effective solution for a relatively small number of heating elements, one problem with such an approach is that at least one additional contact terminal is required for each additional heating element which is to be individually driven. As a consequence, if a larger number of heating elements is required (to create more complex or more uniform temperature profiles), the number of contact terminals may become prohibitively large, making the device unacceptably large and cumbersome. It would also be possible to implement several of the embodiments using other active matrix thin film switching technologies such as diodes and MIM (metal-insulator-metal) devices.

6) Driving Circuits with Oscillators for Biomolecule/Fluid Manipulation

While it is possible to simply incorporate a switch at the heating electrode HE that is to be switched, it is often beneficial to incorporate a frequency oscillator on the glass at each heating electrode HE. This is especially true for trapping of biomolecules as high frequencies (>1 MHz) are often necessary for small particle confinement and with local frequency oscillators the line capacitance is no longer relevant (thus allowing higher frequencies and significantly reducing power dissipation). In addition, it makes it possible to use higher resistance transparent electrodes like transparent oxides, as again the RC delay and power is low.

According to the schematic design shown in FIG. 18, each field electrode used for particle manipulation will be associated with an active matrix circuit which comprises an addressing element, a memory function, an oscillating element, optionally a driving function, and one or more electrodes. Of these functions, the addressing element may be a simple switch, or a more complicated switch in case the same electrode is used for temperature control and biomolecule/fluid actuation (see above), and the memory function may be a storage capacitor.

There are many methods of producing a tunable oscillator. One class of oscillators, known as relaxation oscillators, is frequency tunable by altering the current supplied to the integrated electronics; an example of this class of oscillators is shown in FIG. 20. Here, the rate at which the data current fills the switching capacitor C determines the oscillation frequency. An advantage of this oscillator embodiment is that all TFTs have the same polarity, which makes the circuit also implementable in a-Si technology.

In this class of oscillators, the current required to set the oscillator frequency could be directly supplied by the data driving circuits and mirrored onto the pixel using the circuits shown in FIGS. 20 and 21. The operation of the circuit in FIG. 20 is as follows:

SAMPLE: close S1 and S2; a current I₁ flows in T1 and a current I₂ (=k·I₁) flows in T2 and the oscillator.

HOLD: open S1 and S2; the current I₂ continues to flow in T2 and the oscillator.

The operation of the circuit in FIG. 21 is as follows: 1. Close T1 and T2, current I₁ flows in T4.

2. Open T1 and T2.

3. Close T3, current I₁ now flows in T4 and oscillator.

While FIG. 20 shows a traditional current mirror circuit, in FIG. 21 the current mirror uses the same transistor T4 for sampling the data driver current and driving the oscillator. This single TFT current mirror circuit has the advantage that it is self compensating, and corrects for any variations in the TFT characteristics (such as mobility and threshold voltage). This is important if p-Si TFTs are being used, as here considerable mobility (5-10%) and threshold voltage (+/−1V) variations are found. Any non-uniformity in drive current will be reflected in an equivalent shift in the oscillator frequency.

Alternatively, the data could be addressed in the form of a voltage, and the voltage converted to the required current at a pixel level, using the current source circuits shown in FIGS. 22 and 23. In these circuits, the data voltage is applied to the gate of the current source TFT, and its transconductance characteristic is used to define the current (the current increases as the source-gate voltage gets larger). FIG. 23 shows an improved version of the basic circuit, which is much less sensitive to horizontal cross talk (a decrease in output current when moving across the substrate due to voltage drops along the power line).

If both n-type and p-type transistors are available (for example p-Si technology, or CMOS technology), it is possible to produce oscillators with less TFTs. This is advantageous for the open space (aperture) on the substrate which can be used for rear illumination and detection. Examples of such oscillators can be found in electronics reference books.

Relaxation oscillators of the type shown in FIG. 21 usually have the characteristic that the amplitude of the output signal changes with the output frequency. For many applications it will be necessary to either ensure a constant amplitude output voltage or, more generally, to ensure that the output voltage is variable, independent of the frequency. Both of these situations can be achieved by using output buffers, and these form preferred embodiments of the invention. An example of an implementation of the relaxation oscillator of FIG. 19 with a constant output voltage buffer is given in FIG. 24. In this Figure, the actual implementation of the circuit in p-Si is given (i.e. current sources and resistances are defined by TFTs). The circuit components are furthermore dimensioned to provide oscillation in the 300 Hz-10 kHz bandwidth though the choice of other components would allow other bandwidths. An example of a pixel circuit where the frequency and amplitude of the output voltage are independently variable is shown in FIG. 25. This pixel circuit will require two data signals, one for the frequency (current) and one for the pixel voltage (voltage).

A further class of oscillator circuit which can be implemented in a local tunable oscillator pixel circuit is a ring oscillator. An example of this class of oscillator is shown in FIG. 26. In this example, the frequency and amplitude of the output voltage are independently variable. Again, the circuit components are dimensioned to provide oscillation in the 300 Hz-10 kHz bandwidth as was required for display application. By choosing other components this bandwidth can be altered.

In most cases, the output of the oscillator (a voltage) will directly be used to drive the electrode. In some cases, the electrode will require an oscillating output current. This can again be achieved by converting the oscillating output voltage to a current by using (for example) the transconductance characteristics of a current source TFT, as already shown in FIGS. 22 and 23.

In the above description of the drawings, reference is made to transistors in general. In practice, the temperature controlled cell-array is suited to be manufactured using Low Temperature Poly-Silicon (LTPS) Thin Film Transistors (TFT). Therefore, in a preferred embodiment, the transistors referred to above may be TFTs. In particular, the array may be manufactured on a large area glass substrate using LTPS technology, since LTPS is particularly cost effective when used for large areas.

Further, although the present invention has been described with regard to low temperature poly-Si (LTPS) based active matrix device, amorphous-Si thin film transistor (TFT), microcrystalline or nano-crystalline Si, high temperature poly SiTFT, other anorganic TFTs based upon e.g. CdSe, SnO or organic TFTs may be used as well. Similarly, MIM, i.e. metal-insulator-metal devices or diode devices, for example using the double diode with reset (D2R) active matrix addressing methods, as known in the art, may be used to develop the invention disclosed herein as well.

A programmable temperature processing array as it was described in numerous embodiments above would be an extremely important component of a range of devices aimed at medical and health and wellness products. A main application is to use a temperature processing array in a biochip, such as underneath a biosensor or underneath reaction chambers, where controlled heating provides functional capabilities, such as mixing, thermal denaturation of proteins and nucleic acids, enhanced diffusion rates, modification of surface binding coefficients, etc. A specific application is DNA amplification using PCR that requires reproducible and accurate multiplexed (i.e. parallel and independent) temperature control of the array elements. Other applications could be for actuating MEMS related devices for pressure actuation, thermally driven fluid pumping etc.

Finally it is pointed out that in the present application the term “comprising” does not exclude other elements or steps, that “a” or “an” does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope. 

1. A microelectronic device for manipulating a sample, comprising: a) a sample chamber; b) at least one heating electrode for exchanging heat with at least a sub-region of the sample chamber when being driven with electrical energy; c) at least one field electrode for generating an electrical field in said sub-region of the sample chamber when an electrical potential is applied to it; d) a control unit for selectively driving the electrodes.
 2. The microelectronic device according to claim 1, characterized in that the heating electrode is disposed in a first layer, called “heating layer”, and the field electrode is disposed in a second layer, called “field layer”, said layers being arranged one upon the other adjacent to the sample chamber.
 3. The microelectronic device according to claim 2, characterized in that the field layer is disposed between the sample chamber and the heating layer.
 4. The microelectronic device according to claim 2, characterized in that the heating layer and the field layer each comprise a plurality of heating electrodes and field electrodes, respectively, wherein the electrodes of different layers are preferably aligned with respect to each other.
 5. The microelectronic device according to claim 4, characterized in that the field electrodes are at least partially disposed above gaps between the heating electrodes.
 6. The microelectronic device according to claim 4, characterized in that the field electrodes are at least partially disposed above the heating electrodes.
 7. The microelectronic device according to claim 4, characterized in that the field electrodes are at least partially arranged at an angle, preferably a right angle, to the heating electrodes.
 8. The microelectronic device according to claim 1, characterized in that it comprises an array of heating electrodes.
 9. The microelectronic device according to claim 8, characterized in that the control unit is located outside the array and connected to the heating electrodes by power lines for selectively carrying electrical energy.
 10. The microelectronic device according to claim 9, characterized in that the control unit comprises a de-multiplexer for coupling it to the power lines.
 11. The microelectronic device according to claim 8, characterized in that each heating electrode is associated with a local driving unit.
 12. The microelectronic device according to claim 11, characterized in that all local driving units are coupled to a common power line and that all heating elements are coupled to another common power line.
 13. The microelectronic device according to claim 8, characterized in that a part of the control unit is located outside the array and connected to local driving units, which are located at and coupled to the heating electrodes, via control lines for carrying control signals.
 14. The microelectronic device according to claim 13, characterized in that control signals are pulse-width modulated, pulse-amplitude modulated, and/or pulse frequency modulated.
 15. The microelectronic device according to claim 13, characterized in that the local driving units comprise a memory for storing the information of the control signals.
 16. The microelectronic device according to claim 1, characterized in that the field electrode is a bi-functional electrode, which can by definition also be operated like a heating electrode.
 17. The microelectronic device according to claim 16, characterized in that it comprises several field electrodes which all are bi-functional electrodes.
 18. The microelectronic device according to claim 16, characterized in that the control unit is adapted to drive the bi-functional electrode simultaneously and/or sequentially like a field electrode and like a heating electrode.
 19. The microelectronic device according to claim 16, characterized in that the bi-functional electrode is connected with one pole to a first potential and, via a switch controlled by the control unit, with its second pole to a distinct second potential.
 20. The microelectronic device according to claim 1, characterized in that it comprises at least two field electrodes which commonly generate an electrical field in said sub-region of the sample chamber when an electrical voltage is applied between them. 21-48. (canceled) 